/Engine/Source/Runtime/Engine/Classes/Engine/DamageEvents.h
This is for compatibility with old-style functions which want a unified set of hit data regardless of type of hit. Ideally this will go away over time.
virtual void GetBestHitInfo ( [AActor](API\Runtime\Engine\GameFramework\AActor) const * HitActor, [AActor](API\Runtime\Engine\GameFramework\AActor) const * HitInstigator, [FHitResult](API\Runtime\Engine\Engine\FHitResult) & OutHitInfo, FVector & OutImpulseDir ) const